Spin finish, spinning finish, dressing, treating agent, spinning lubricant, coating fiber finish, processing agent, textile treating agent, textile treating composition, conditioning agent--all of these terms are used to designate the same material: an antistatic lubricant applied to the surface of man-made fibers as soon as practical after the fiber has been formed. The properties of the applied material are dictated by several factors, among which are the fiber to which it is applied and the processing to which the fiber is to be subjected. In general, once the fiber has been converted into yarn and then into fabric, the role of the finish is complete; it is usually removed prior to or during dyeing.
Natural fibers have their own finish. Cotton, for example, has a wax coating. The crude material extracted from raw cotton fiber by chloroform, carbon tetrachloride, benzene, or other organic solvents is usually called wax. Presumably most of the wax is located in the cuticle, which lies on the outside of the fiber. Most cotton which is spun contains its natural wax. Dewaxed cotton does not spin well. The wax undoubtedly has desirable lubricating properties for spinning.
In the production of synthetic continuous filament yarns, it is necessary to apply to the filaments during the spinning operation a lubricating composition to reduce friction developed as the yarns pass over the metal and ceramic machinery surfaces. Since they are applied during the spinning step, they are frequently referred to as spin finishes. Such finishes usually contain a lubricating ingredient to reduce friction, an antistatic agent to reduce the build-up of static electrical charges on the surfaces of the yarn as it passes over various machinery components, an antioxidant or thermal stabilizing agent to reduce the build-up of resin deposits on the machinery and the yarn itself, and an emulsifying agent in order that the total system may be applied to the yarn from an aqueous emulsion.
The primary function of a finish is to provide surface lubricity to the yarn such that smooth high-speed transfer over various metallic guides can take place with a minimum of fiber breakage.
Finishes also bring about fiber to fiber cohesiveness which is necessary to maintain uniform diameter and uniform twist configurations in the continuous multi-filament yarn system and winding.
Most synthetic fibers, due to their hydrophobic nature, are static prone--that is, they demonstrate a marked tendency to retain electrostatic charges. During the processing of the yarn, high-speed operations accelerate generation and retention of electrostatic charges. Without static protection of yarn, several problems may occur thereto such as ballooning of yarn due to like charge repulsion between individual filaments, and tactile shock upon contact with processing equipment.
The electrostatic charges occurring on synthetic fibers may sometimes be disturbing to such a degree that they strongly impede or render completely impossible the further processing of the fibers.
To minimize wear and tear, heat damage, accumulation of static charges, and other like processing headaches, it has been found advantageous to enhance interfilament friction characteristics and fiber bundle cohesion generally by the use of finishes.
In preparation of yarns suitable for textile manufacture it is necessary to apply a lubricant to the filaments to permit processing of the yarn with minimum difficulty. As is well known in the art, selection of a suitable lubricant composition is not readily made, since many diverse requirements are imposed on the lubricant composition by the nature of a yarn's use and the manner in which it is manufactured. Of particular concern in high-temperature processing is the formation of hard insoluble resins and the fuming of the finish when contacting heated surfaces. Some earlier attempts at providing spin fiber lubricants are referred to below.